The safety case and the lessons learned for the reliability and maintainability case

This paper examine the safety case and the lessons learned for the reliability and maintainability case

Design and Implementation of a True Decentralized Autonomous Control Architecture for Microgrids

Microgrids can serve as an integral part of the future power distribution systems. Most microgrids are currently managed by centralized controllers. There are two major concerns associated with the centralized controllers. One is that the single controller can become performance and reliability bottleneck for the entire system and its failure can bring the entire system down. The second concern is the communication delays that can degrade the system performance. As a solution, a true decentralized control architecture for microgrids is developed and presented. Distributing the control functions to local agents decreases the possibility of network congestion, and leads to the mitigation of long distance transmission of critical commands. Decentralization will also enhance the reliability of the system since the single point of failure is eliminated. In the proposed architecture, primary and secondary microgrid controls layers are combined into one physical layer. Tertiary control is performed by the controller located at the grid point of connection. Each decentralized controller is responsible of multicasting its status and local measurements, creating a general awareness of the microgrid status among all decentralized controllers. The proof-of concept implementation provides a practical evidence of the successful mitigation of the drawback of control command transmission over the network. A Failure Management Unit comprises failure detection mechanisms and a recovery algorithm is proposed and applied to a microgrid case study. Coordination between controllers during the recovery period requires low-bandwidth communications, which has no significant overhead on the communication infrastructure. The proof-of-concept of the true decentralization of microgrid control architecture is implemented using Hardware-in-the-Loop platform. The test results show a robust detection and recovery outcome during a system failure. System test results show the robustness of the proposed architecture for microgrid energy management and control scenarios

Reliability Evaluation of Common-Cause Failures and Other Interdependencies in Large Reconfigurable Networks

This work covers the impact of Interdependencies and CCFs in large repairable networks with possibility of "re-configuration" after a fault and the consequent disconnection of the faulted equipment. Typical networks with these characteristics are the Utilities, e.g. Power Transmission and Distribution Systems, Telecommunication Systems, Gas and Water Utilities, Wi Fi networks. The main issues of the research are: (a) Identification of the specific interdependencies and CCFs in large repairable networks, and (b)Evaluation of their impact on the reliability parameters (load nodes availability, etc.). The research has identified (1) the system and equipment failure modes that are relevant to interdependencies and CCF, and their subsequent effects, and (2) The hidden interdependencies and CCFs relevant to control, supervision and protection systems, and to the automatic change-over systems, that have no impact in normal operation, but that can cause relevant out-of-service when the above automatic systems are called to operate under and after fault conditions. Additionally methods were introduced to include interdependencies and CCFs in the reliability and availability models. The results of the research include a new generalized approach to model the repairable networks for reliability analysis, including Interdependencies/CCFs as a main contributor. The method covers Generalized models for Nodes, Branches and Load nodes; Interdependencies and CCFs on Networks / Components; System Interdependencies/CCFs; Functional Interdependencies/CCFs; Simultaneous and non-simultaneous Interdependencies/CCFs. As an example detailed Interdependency/CCFs analysis and generalized model of an important network structure (a "RING" with load nodes) has been analyzed in detail

Predicting The Reliability Of A Repairable System With Competing Failure Modes

The main objective of this project is to analyze the failure data of centrifugal pumps that were provided by a petrochemical plant and to develop a reliability model to predict the failure occurrences for each failure modes

Fault-tolerant computer study

A set of building block circuits is described which can be used with commercially available microprocessors and memories to implement fault tolerant distributed computer systems. Each building block circuit is intended for VLSI implementation as a single chip. Several building blocks and associated processor and memory chips form a self checking computer module with self contained input output and interfaces to redundant communications buses. Fault tolerance is achieved by connecting self checking computer modules into a redundant network in which backup buses and computer modules are provided to circumvent failures. The requirements and design methodology which led to the definition of the building block circuits are discussed

Optimal configuration of a power grid system with a dynamic performance sharing mechanism

Performance sharing is an effective policy for a power grid system to satisfy the power demand of different districts to greatest extent. Through transmission lines, the districts with sufficient power can share the redundant power with the districts with power deficit. The existing research has incorporated the performance sharing mechanism into systems with simple structures such as parallel systems and series-parallel systems. However, little concentration has been spent on more complex structures. This necessitates the need of this paper that models a power distribution with a more complex reliability structure. We assume that the system is composed of generators and nodes. Both the performance of each generator and the demand of each node in the network are assumed to be random variables. This paper first proposes a dynamic performance sharing policy to minimize the unsupplied demand for a given system with fixed capacity and demand. The optimal allocation of generators, which minimizes the expected system unsupplied demand, is then studied. Numerical examples are proposed to illustrate the applications of the proposed procedures

ISBIS 2016: Meeting on Statistics in Business and Industry

This Book includes the abstracts of the talks presented at the 2016 International Symposium on Business and Industrial Statistics, held at Barcelona, June 8-10, 2016, hosted at the Universitat Politècnica de Catalunya - Barcelona TECH, by the Department of Statistics and Operations Research. The location of the meeting was at ETSEIB Building (Escola Tecnica Superior d'Enginyeria Industrial) at Avda Diagonal 647. The meeting organizers celebrated the continued success of ISBIS and ENBIS society, and the meeting draw together the international community of statisticians, both academics and industry professionals, who share the goal of making statistics the foundation for decision making in business and related applications. The Scientific Program Committee was constituted by: David Banks, Duke University Amílcar Oliveira, DCeT - Universidade Aberta and CEAUL Teresa A. Oliveira, DCeT - Universidade Aberta and CEAUL Nalini Ravishankar, University of Connecticut Xavier Tort Martorell, Universitat Politécnica de Catalunya, Barcelona TECH Martina Vandebroek, KU Leuven Vincenzo Esposito Vinzi, ESSEC Business Schoo

Developmental Flight Test Lessons Learned from Open Architecture Software in the Mission Computer of the U.S. Navy E-2C Group II Aircraft

The Naval Air Systems Command commissioned the E-2C Hawkeye Group II Mission Computer Replacement Program and tasked Air Test and Evaluation Squadron Two-Zero and the E-2C Integrated Test Team to evaluate the integration of the form, fit, and function of the OL-698/ASQ Mission Computer Replacement (MCR) for replacement of the Litton L-304 Mission Computer in the E-2C Group II configured aircraft. As part of the life cycle support of the E-2C aircraft, the MCR configuration fields a new, more reliable Commercial-off-the-Shelf (COTS) hardware system and preserves the original software investment by emulating the existing Litton Instructional Set Architecture (LISA) legacy code. Incorporating Northrop Grumman Space Technology’s Reconfigurable Processor for Legacy Applications Code Execution (RePLACE) software re-hosting technique, the investment in the LISA software is maintained. Conducting developmental test of robust software systems, such as the MCR and its associated software, provided dramatically different challenges than traditional developmental testing. A series of lessons were learned through particular discrepancies and deficiencies discovered through the six month flight test period. Specific deficiencies illustrate where proper planning could ease the difficulties encountered in software testing. Keys to successful developmental software tests include having the appropriate personnel on the test team with the proper equipment and capability. Equally important, inadequate configuration management creates more problems than fixes. Software re-programming can provide faster fixes than traditional developmental test. The flexibility of software programming makes configuration management a challenge as multiple versions become available in a short amount of time. Multiple versions of software heighten the risk of configuration management breakdown during limited amount of available flight tests. Each re-programmed version potentially fixes targeted deficiencies, but can also cause new issues in functional areas already tested. Inherently, regression testing impacts the schedule. Software testing requires a realistic schedule that the author believes should compensate for anticipated problems. Data collection, reduction, and analysis always prove to be valuable in developmental testing. A solid instrumentation plan for data collection from all parties involved in flight tests, especially data link network tests, are critical for trouble shooting discovered deficiencies. Software testing is relatively new to the developmental test world and can be seen as the way of the future. Software upgrades lure program managers into a potentially cost effective option in the face of aging avionics systems. With realistic planning and configuration management, the cost and performance effectiveness of software upgrades and development is more likely to become realized